The present invention relates to a method for controlling a steering apparatus.
The closest prior art is disclosed in German Patent Application DE 10 2008 021 849 A1. This document shows a steering device for a road vehicle which is servo-assisted by electric motor driving a steering rack via a belt drive. The device comprises a number of sensors, namely a steering angle sensor which is associated with the steering wheel and a motor position sensor which detects the position of the rotor of the electric motor. The system continuously checks the relationship between the motor position and the steering angle. Among other features, a belt lump detection is provided which detects a sudden offset in the correlation between the steering angle and the motor position. Such an offset can occur in the case of belt driven electromechanical steering systems if the belt is a toothed belt and due to an overload situation, the belt slips on the belt gear and jumps from one to another. The prior art system will in this case assume that the belt has been damaged and the steering operates in a mode which prevents further damage to the belt, namely by reducing the servo-assistance.
While the prior art steering systems provide the driver with an information that the belt may be damaged and has to be checked, there is no information whether or not the mechanical components of the steering linkage (tie rods etc.) and the suspension have been damaged. The prior art systems do not monitor the center position of the steering system and the actual position of the steering rack while driving straight ahead.
It is therefore am object of the present invention to provide a method for controlling an electromechanical steering system which comprises a further detection of possible damages to the steering system and to the suspension.